1 /* 2 * ==================================================== 3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 4 * 5 * Developed at SunPro, a Sun Microsystems, Inc. business. 6 * Permission to use, copy, modify, and distribute this 7 * software is freely granted, provided that this notice 8 * is preserved. 9 * ==================================================== 10 */ 11 12 /* 13 * floorl(x) 14 * Return x rounded toward -inf to integral value 15 * Method: 16 * Bit twiddling. 17 * Exception: 18 * Inexact flag raised if x not equal to floorl(x). 19 */ 20 21 #include <float.h> 22 #include <math.h> 23 #include <stdint.h> 24 25 #include "fpmath.h" 26 27 #ifdef LDBL_IMPLICIT_NBIT 28 #define MANH_SIZE (LDBL_MANH_SIZE + 1) 29 #define INC_MANH(u, c) do { \ 30 uint64_t o = u.bits.manh; \ 31 u.bits.manh += (c); \ 32 if (u.bits.manh < o) \ 33 u.bits.exp++; \ 34 } while (0) 35 #else 36 #define MANH_SIZE LDBL_MANH_SIZE 37 #define INC_MANH(u, c) do { \ 38 uint64_t o = u.bits.manh; \ 39 u.bits.manh += (c); \ 40 if (u.bits.manh < o) { \ 41 u.bits.exp++; \ 42 u.bits.manh |= 1llu << (LDBL_MANH_SIZE - 1); \ 43 } \ 44 } while (0) 45 #endif 46 47 static const long double huge = 1.0e300; 48 49 long double 50 floorl(long double x) 51 { 52 union IEEEl2bits u = { .e = x }; 53 int e = u.bits.exp - LDBL_MAX_EXP + 1; 54 55 if (e < MANH_SIZE - 1) { 56 if (e < 0) { /* raise inexact if x != 0 */ 57 if (huge + x > 0.0) 58 if (u.bits.exp > 0 || 59 (u.bits.manh | u.bits.manl) != 0) 60 u.e = u.bits.sign ? -1.0 : 0.0; 61 } else { 62 uint64_t m = ((1llu << MANH_SIZE) - 1) >> (e + 1); 63 if (((u.bits.manh & m) | u.bits.manl) == 0) 64 return (x); /* x is integral */ 65 if (u.bits.sign) { 66 #ifdef LDBL_IMPLICIT_NBIT 67 if (e == 0) 68 u.bits.exp++; 69 else 70 #endif 71 INC_MANH(u, 1llu << (MANH_SIZE - e - 1)); 72 } 73 if (huge + x > 0.0) { /* raise inexact flag */ 74 u.bits.manh &= ~m; 75 u.bits.manl = 0; 76 } 77 } 78 } else if (e < LDBL_MANT_DIG - 1) { 79 uint64_t m = (uint64_t)-1 >> (64 - LDBL_MANT_DIG + e + 1); 80 if ((u.bits.manl & m) == 0) 81 return (x); /* x is integral */ 82 if (u.bits.sign) { 83 if (e == MANH_SIZE - 1) 84 INC_MANH(u, 1); 85 else { 86 uint64_t o = u.bits.manl; 87 u.bits.manl += 1llu << (LDBL_MANT_DIG - e - 1); 88 if (u.bits.manl < o) /* got a carry */ 89 INC_MANH(u, 1); 90 } 91 } 92 if (huge + x > 0.0) /* raise inexact flag */ 93 u.bits.manl &= ~m; 94 } 95 return (u.e); 96 } 97